Developmental Longitudinal and Cross Sectional Survey:
Suppose, you wish to study the growth and development pattern of children from birth tofive years of age. This is an example of development research. This studycan be done in two ways. One, the researcher can follow a group of new born infants from their birth to five years of age to assess aspects of their growth and development patterns. This is called as longitudinal survey. The second method is a cross sectional survey where the researcher for example takes representative samples fiom the age groups of birth-three months, four-six months, seven, nine months, and so on till the sixteenth month. Both methods have certain advantages and disadvantages. Let us examine them.
In longitudinal survey sequence of events is observed in each subject selected for the study. Data here is more objective as the subjects do not have to recall for reply. The most difficult part of this study is to keep contact with the subjects as the individuals may move out of the place of residence or drop out of the study. This is called as the subject mortality. For this reason a large number of subjects is needed for desired sample size in the end of the study. It takes a long time to know the final results. Many a time cross-sectional study is done in place of longitudinal study. Advantages are that it can be completed in a relatively short time and is relatively less expensive; sample loss is less than longitudinal study; and the results are known early. The disadvantage. is that the method can only consider the present and past and not the future as in longitudinal study. So, trends and patterns over a period of time can not be described.
The case study and retrospective survey (or ex-post facto) are two other methods which are sometimes included as types oi survey method or sometimes are treated separately. However, we are discussing them under survey.